And then there's the much-talked-about bit where she appears to be sitting naked in the front seat of car and using her hands to pleasure Hedlund and Riley at the same time.

To be fair, Stewart is not the only one who is pushing the envelope in the movie. Hedlund also appears naked (the first shot of him is of his bare bum) and having sex and doing drugs—a lot. He shares a passionate kiss with Tom Sturridge, who plays Carlo Marx (aka poet Allen Ginsberg), and even has a sex scene with—get ready for it!—Boardwalk Empire star Steve Buscemi.

Even so, the sex, drugs and naughtiness are not gratuitous. Like Kerouac's semi-autobiographical novel, On the Road captures both the genius and the recklessness of the Beat Generation.

In other words, this film may not be suitable for Twi-hards of all ages.